The invention relates to a novel process for the preparation of 4-(4'-chlorobiphenyl-4-yl)-4-keto-2-methylenebutyric acid of the formula (I) below.
4-(4'-Chlorobiphenyl-4-yl)-4-keto-2-methylenebutyric acid is an important intermediate for the synthesis of matrix metalloendoproteinase inhibitors (MMP), which are employed as active compounds for the prevention of the metastasis of malignant tumors. The compound, however, is prone to isomerization to give conjugated isomers. This reaction is induced by traces of base, strong acids and thermal stress.
On account of the importance of 4-(4'-chlorobiphenyl-4-yl)-4-keto-2-methylenebutyric acid of the formula (I), a large number of procedures for the preparation of this compound exist. All known syntheses of the compound start from 4-chlorobiphenyl of the formula (II), which is reacted with AlCl.sub.3 and itaconic anhydride of the formula (III). ##STR2##
J.-P. Rieu et al. (J. Pharm. Sci. 1980, 69, 49) carry out the reaction in the solvent dichloromethane. After aqueous work-up, removal of the solvent by distillation and recrystallization from an 11-fold volume of ethyl acetate, the product is obtained in a yield of only 52%.
H. Cousse et al. (Eur. J. Med. Chem. 1987, 22, 45-57) use 1,2-dichloroethane or dichloromethane as a solvent. After aqueous work-up, the organic phase is mixed with ethanol and acetone, whereupon the product precipitates, and is filtered off with suction and recrystallized. The yields indicated are, however, only 46%.
In DE-A-25 13 157 too, biphenyls and halobiphenyls are acylated with itaconic anhydride according to Friedel-Crafts in the presence of a Lewis acid catalyst. The solvent used here is the strongly toxic 1,1,2,2-tetrachloroethane. Yields for the acylation of 4-chlorobiphenyl are not indicated.